PHYLOGENETIC ANALYSES OF POLEMONIACEAE USING NUCLEOTIDE-SEQUENCES OF THE PLASTID GENE MATK

Nucleotide sequences of the plastid encoded gene matK were examined for their potential utility in phylogenetic analyses within angiosperm families. Sequences 661 bases in length were obtained from twenty species of Polemoniaceae. Phylogenetic analyses resulted in four equally parsimonious trees with a consistency index of 0.70. Several well supported groups allowed us to test hypotheses of relationship within Polemoniaceae. The segregation of Ipomopsis and Allophyllum from Gilia was supported by the placement of each in distinct groups separate from a group of four species of Gilia. Several strongly supported groups include genera now placed in different tribes. There was no support for the current separation of temperate Polemoniaceae into two tribes. The tropical genera were resolved as basal and paraphyletic within the family. The family as a whole was monophyletic with no support for the segregate family Cobaeaceae. Sequences of matK, a gene that had not been used previously for phylogenetic analyses, provided a sufficient number of reliable characters for phylogenetic analysis within Polemoniaceae. Pairwise comparisons of matK and rbcL sequences of the same taxa were performed. Sequences of matK varied at an overall rate twice that of rbcL sequences. Substitutions at the third codon position predominated in rbcL sequences, while in matK substitutions were more evenly distributed across codon positions.